U.S. patent number 4,507,640 [Application Number 06/444,637] was granted by the patent office on 1985-03-26 for high frequency transformer.
This patent grant is currently assigned to Westinghouse Electric Co.. Invention is credited to Edward L. Rich, III, Yucel Y. Yalim.
United States Patent |
4,507,640 |
Rich, III , et al. |
March 26, 1985 |
High frequency transformer
Abstract
A high frequency, transformer capable of operating at high power
levels is disclosed. Conductive ribbons including end (terminal)
sections which permit the terminal leads of a plurality of windings
to be extended from the windings in an overlapping relationship and
in the selected order is utilized for the windings. Preferably, the
core is formed of a material having low eddy current losses and
characteristics permitting the core to be molded such that the
windings are substantially surrounded by the core with the
exception of small openings through which the leads extend.
Inventors: |
Rich, III; Edward L. (Arnold,
MD), Yalim; Yucel Y. (Coral Springs, FL) |
Assignee: |
Westinghouse Electric Co.
(Pittsburgh, PA)
|
Family
ID: |
23765715 |
Appl.
No.: |
06/444,637 |
Filed: |
November 26, 1982 |
Current U.S.
Class: |
336/223; 336/232;
336/83 |
Current CPC
Class: |
H01F
19/04 (20130101); H01F 17/043 (20130101) |
Current International
Class: |
H01F
17/04 (20060101); H01F 19/00 (20060101); H01F
19/04 (20060101); H01F 027/28 () |
Field of
Search: |
;336/83,223,232 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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|
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|
|
1230874 |
|
Dec 1966 |
|
DE |
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2406353 |
|
Nov 1974 |
|
DE |
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4529950 |
|
Dec 1967 |
|
JP |
|
Primary Examiner: Pellinen; A. D.
Assistant Examiner: Steward; Susan A.
Attorney, Agent or Firm: Hinson; J. B.
Claims
We claim:
1. A transformer comprising in combination:
(a) a core, said core including first and second sections each
having a first substantially flat end and a second end, said second
end including a groove surrounding a central portion and an outer
portion separated from said central portion by said groove, said
second end of said first and second sections adjacently positioned
defining a closed magnetic path;
(b) a plurality of windings each encircled by said closed magnetic
path, each winding comprising a substantially flat electrically
conductive ribbon selectively covered with an electrically
insulating layer, each ribbon having a central portion, a
connecting portion and a terminal portion, said connecting portion
joining said central and said terminal portions such that said
terminal portion is substantially parallel to said central portion
and off-set thereform permitting a plurality of said ribbons to be
wound such that the edges of said plurality of ribbons are in
substantially the same plane to form windings with said connecting
portions being folded over the edge of said windings with said
terminal portions emerging from said windings in a selected order
such that the edges of said terminal portions are in substantially
the same plane.
2. A ribbon for use as a winding for a transformer comprising:
(a) a central portion having substantially straight and parallel
edges;
(b) at least one terminal portion having substantially straight and
parallel edges;
(c) at least one interconnecting portion coupling said central
portion and said at least one terminal portion together such that
said edges of said central and edge portions are substantially
parallel to each other thereby permitting a plurality of said
ribbons to be wound such that the edges of said ribbons are in
substantially the same plane to form a winding with said
interconnecting portion being folded over the edge of said winding
such that said terminal portions emerge from said winding in a
selected order.
3. A ribbon for winding a transformer comprising:
(a) first and second end portions each having substantially
straight and parallel edges;
(b) a central narrow portion, formed by a notch in said ribbon,
having a width less than said end portion permitting at least two
of said ribbons to be interleaved by positioning the narrow portion
of said first winding in the notch in said second winding and by
also positioning the narrow portion of said second winding in the
notch in said first winding such that when said ribbons ae used to
form a transformer winding the ends of said windings can be
interconnected to form a single center tapped winding with the
center terminal of said center tapped winding being positioned
between the end terminals of said center tapped winding.
4. A transformer comprising:
(a) a magnetic structure having two substantially identical
sections each having a substantially flat first end, a second end
including a groove surrounding a central portion and an outer
portion separated from said central portion by said groove, one
edge of said outer portion defining the outer edge of said groove
such that when said second end of said two sections are positioned
adjacent each other said central and outer portions are in contact,
thereby forming a cavity surrounded by a magnetic circuit formed by
said first and second substantially identical sections;
(b) a first electrically conductive ribbon having the surface
thereof selectively covered with an electrically insulating layer,
said electrically conductive ribbon also including a central
portion, a terminal portion and a connecting portion joining said
central and terminal portions such that said terminal portions is
off-set from said central portions with the edges of said central
and terminal portions substantially parallel;
(c) a second electrically conductive ribbon having the surface
thereof selectively covered with an electrically insulating layer,
said electrically conductive ribbon also including a central
portion, a terminal portion and a connecting portion joining said
central and terminal portions such that said terminal portions is
off-set from said central portions with the edges of said central
and terminal portions are substantially parallel; with:
(d) said first and second electrically conductive ribbons being
wound such that the edges of said central portions of said first
and second electrically conductive ribbons are in substantially the
same plane to form a winding with said connecting portions being
folded over the edge of said winding such that when said winding is
positioned in said cavity said end portions emerge through said
outer portions of said magnetic structure in a selected order.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to transformers and more specifically to high
frequency, high current transformers utilizing ribbon conductors as
the windings.
2. Description of the Prior Art
Prior art high frequency transformers were limited in currrent
capability due to the resistance of the wire utilized as conductors
at high (RF) frequencies as well as by a stray inductance
associated with the input leads and the windings. Additionally,
some of these effects such as the stray inductance associated with
the leads tended to be variable because the coupling between the
leads as well as from the leads to other structures in the vicinity
was rather unpredictable.
The net external lead loop area, resulting from leads not emerging
in preferred positions, often caused a limiting amount of leakage
inductance (100's of nanohenries).
SUMMARY OF THE INVENTION
The preferred embodiment of the invention utilizes a magnetic core
formed in at least two sections, the sections defining a magnetic
path which surrounds the windings except for openings through which
the leads extend. Conductive ribbons are utilized as windings and
include end sections which permit the leads associated with a
plurality of windings to be brought out in a preferred order and
such that they are in a layered arrangement. (Layered arrangement
is intended to indicate that the leads are stacked with the edges
of the ribbons being substantially parallel to each other with
insulating layers separating the ribbons from each other.)
In an alternate embodiment, the magnetic core includes an opening
in the center through which the ribbon leads extend.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a drawing illustrating a completed transformer in
accordance with the invention;
FIG. 2 is an isometric drawing illustrating one section of the two
section core utilized by the transformer which is the subject of
the invention;
FIGS. 3-7 are electrically conductive ribbons utilized as windings
in various embodiments of the invention;
FIG. 8 is a partial isometric drawing illustrating the use of the
end sections of the electrically conductive ribbons;
FIG. 9 is a top view of a completed winding;
FIG. 10 is a drawing illustrating an electrically conductive ribbon
utilized to wind transformers having leads extending through the
center of the core;
FIG. 11 is an isometric view of an alternate embodiment of a
transformer comprising the invention;
FIG. 12 is a cross-section view of the transformer illustrated in
FIG. 11; and
FIGS. 13 and 14 are drawings of alternate ribbons which may be used
as windings.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
FIG. 1 is a drawing illustrating a transformer having four
independent windings in accordance with the preferred embodiment of
the invention. The preferred embodiment includes a two-piece pot
core 22. Continuous electrically conductive ribbons are utilized as
windings with the ends of the ribbons 24-31 serving as input
connections (leads) to the transformer 20. Other winding
configurations may require more or less input connections.
FIG. 2 is an isometric view of one of the two identical sections
comprising the core 22 of the embodiment illustrated in FIG. 1. In
the art, transformer cores of the type illustrated in FIG. 2 are
known as pot cores and can be purchased commercially from a variety
of suppliers. For high frequency use, such as the transformers
which are the subject of this application, the cores should be
composed of a magnetic material having a low hysteresis and eddy
current losses and high bulk resistivity. Suitable magnetic
materials for such cores are generically called ferrites in the
art.
Structurally, the core 34 includes a cylindrical central portion 36
having an opening 37 in the center thereof. Surrounding the central
portion 36 is a groove 38 bounded on the outer edge by a wall
portion 40. At one end the outer wall 40 and the central portion 36
are joined by a disc-like portion 42 to complete the structure of
the core. Two openings 44 and 46 are provided in the outer wall 40
for leads to extend from the completed transformer 22. Cores of the
type illustrated in FIG. 2 ae suitable for use in all embodiments
of the invention in which the leads extend outward radially through
the outer wall of the core 34. Other core configurations are also
usable provided a suitable magnetic path is maintained.
Various embodiments of the ribbons used to wind the transformers
having leads extending through the openings, 44 and 46 are
illustrated in FIGS. 3-7, 13 and 14. The specific ribbon used
depends on the transformer configuration.
More specifically, FIG. 3 illustrates a first embodiment of the
electrically conductive ribbon. The ribbon includes a central
portion 50 which has two substantially parallel edges and is
insulated electrically on at least one side thereof by an
electrically insulating layer 51. Attached to the central portion
50 and offset therefrom by a selected distance are two (terminal)
end portions 52 and 54, also having substantially parallel edges.
End portions 52 and 54 are joined to the central portion 50 by two
substantially identical sections each having slots, 56, parallel to
the edges thereof. Although the end portions 52 and 54 are
illustrated as offset from the central portion 50 in the same
direction, they may be offset in opposite directions.
A second electrically conductive ribbon which includes a first
portion 60 having parallel edges and a second portion 62 is
illustrated in FIG. 4. The first and second portion 60 and 62 are
joined are jointed by a slotted portion 63 which includes parallel
slots 64. An electrically insulating layer 61 covers the ribbon.
This electrically conductive ribbon is essentially identical to the
one illustrated in FIG. 3 except that it only includes one offset
or end portion.
An embodiment of the ribbon useful in winding center tapped single
turn transformers in accordance with the invention is illustrated
in FIG. 5. This embodiment includes two central portions 66 and 68,
each having substantially parallel edges and an insulating layer 61
on at least one side thereof. Two end (terminal) sections 70 and 72
are connected to the central portions by a region which includes
parallel slots 74 and 76. Intermediate to the first and second end
portions 70 and 72 is a third end (terminal) section 78 which is
coupled to the junction of central portions 66 and 68 by a third
connecting section which also includes parallel slots 80. If this
ribbon is to be used to form a center tapped winding, the central
portions 66 and 69 will be of equal length. If the terminal formed
by the central end (terminal) section 78 this ribbon is located at
a point other than the center, portions 66 and 68 will be of
unequal length resulting in the winding being taped at a point
other than its center.
The ribbons discussed above may be modified such that the end
portions are positioned on opposite sides of the central portion.
Such a modification of the ribbons may require that the ribbons be
pre-wound and then positioned in the core.
Two electrically conductive ribbons which can be utilized to wind a
transformer in which the leads come out in order such that two
adjacent terminals can be connected to form a center tapped
winding, are illustrated in FIGS. 6 and 7. More specifically, a
ribbon 82 having substantially parallel edges and a notch 84 in the
lower edge thereof is illustrated in FIG. 6. A complementary ribbon
86 having a notch 88 in the upper edge thereof is illustrated in
FIG. 7. These two ribbons can be positioned such that the narrow
portion of fibbon 82 is in the notch 88 of ribbon 86 and the narrow
portion of ribbon 86 is in the notch 84 or ribbon 82. The two
ribbons 82 and 86 are then simultaneously wound on the core such
that the two adjacent central terminals can be connected together
to form a center tapped winding. Electrically insulating layers 83
and 87 prevent electrical connections between ribbons 82 and 86
except at the center tap.
FIG. 8 is a fragmentary view of a core 34 of the type illustrated
in detail in FIG. 2 and a portion of a winding illustrating how the
ribbons having offset terminal portions as illustrated in FIGS. 3,
4 and 5 are utilized to form transformer windings. More
specifically, winding 90 includes a ribbon of the type illustrated
in FIG. 3. The same reference numerals used to identify the parts
of the ribbon in the above discussion will be used in this figure
for clarity. For example, the end (terminal) portion 54 of the
ribbon extends through the opening in the outer wall of the core 34
to form a lead to the winding. The slots 56 in the connecting
portion permit the central portion 50 of the ribbon to be on the
interior of the winding 90 and the ribbon to be folded over to the
outside of the winding and positioned such that it extends through
the opening in the core 34 to form a convenient terminal lead. The
other end portions of the ribbons illustrated in FIGS. 3, 4 and 5
can be similarly utilized to form connections to windings similarly
positioned in the core 34. The order in which the windings emerge
from the pot cores to form leads can be controlled by the order in
which the connection portions are folded over to form the leads.
This permits the leads to be brought out in any convenient order.
Of course the ribbon illustrated in FIG. 3 can be utilized only on
the outermost winding with the end not having an offset end portion
being used as the final end of the outermost winding.
The slotted portion 56 of the ribbon 50 is distorted in FIG. 8
because the inner and outer circumferences of the winding 90 are
different. Slots 56 provide sufficient flexibility to permit the
ribbon 54 to be folded over without unreasonable distortion.
Although the electrically conductive ribbons illustrated only two
slots, a different number of slots can be used.
FIG. 9 is a top view of one half of the core 20 having a winding
composed of two ribbons of the type illustrated in FIG. 3 wound
with adjacent leads 73 and 75 connected together to conveniently
form a single tapped winding. A second center tapped winding for
the secondary can be similarly constructed if desired. Other
windings can also be added, as required. Such additional windings
are not illustrated for purposes of convenience.
FIG. 10 illustrates an alternate embodiment of a ribbon 100 which
may be used to wind transformers such that the leads emerge through
an opening in the center of the transformer core. More
specifically, ribbon 100 includes a central portion 102 having
substantially parallel edges and an insulating layer 103 on at
least one side thereof. The ends of the central portion 102
connects to end portions 104 and 106, each having substantially
parallel edges and positioned at substantially 90.degree. with
respect to the central portion 102. Each of the end PG,8 sections
104 and 106 terminates in tabs 108-114. The use of this ribbon to
form a typical winding of a transformer is illustrated in FIG.
11.
FIG. 11 is an isometric view with partial sections illustrating the
use of the ribbon 100 to form a winding of a transformer. The
transformer illustrated in FIG. 11 includes a cup core 116, very
similar to the previous embodiments. The central portion 102 of the
ribbon winds around the cylindrical central portion of the core 116
and extends through slots 105 and 107 in the central portion of the
core 115. The ends portions 106 and 104 of the ribbon 100 extend
radially out through slots 105 and 107 in the core 116 such that
the conductive end tabs 108-114 extend beyond the top and bottom
edges of the core 16. Although only one ribbon is illustrated in
FIG. 11, additional windings can be similarly added to complete the
transformer.
For further clarity, a cross-section along the mating surface of
the two sections of the core 116 of the transformer illustrated in
FIG. 11 is shown in FIG. 12. This figure clearly illustrates the
position of the central portion 102 of the ribbon 100 as well as
the end portions 104 and 106 extending through the slots in the
central portion in the core.
Alternate ribbon configurations useful in winding transformers of
the type illustrated in FIG. 11 are illustrated in FIGS. 13 and 14.
More specifically, the ribbon illustrated in FIG. 13 includes a
central portion 120 and two end tabs 122 and 124 connected to the
central portion 120 by two connecting sections 126 and 126. This
ribbon can be used to form a winding on a core of the type
illustrated at reference number 116, FIG. 11 with both terminals
extending to the top or bottom of the core 116. (It is arbitrary
which surface is considered to be the top or bottom of core
116.)
A further alternate ribbon suitable for forming windings on a core
of the type illustrated at reference number 116 of FIG. 11 is
illustrated in FIG. 14. This ribbon includes a central portion 128
and two end terminals 130 and 132. The end terminals 130 and 132
are coupled to the central portion 128 by first and second
connecting sections 134 and 136. This ribbon can be used to form
windings on the core 116 such that terminals 130 and 132
respectively extend through the top and bottom surfaces of the core
116.
Many additional modifications can be made to the conductive ribbons
specifically discussed. For example, two or more ribbons can be
separated by an insulating layer and laminated together and wound
on the core at the same time. Also, the central portion 102 of the
ribbon illustrated in FIG. 10 can be split along a horizontal line
to form two windings with the terminals of on winding extending
through the top surface of the core and the terminals of the second
winding extending through the bottom surface of the core.
* * * * *